Electric contacting member



Patented Oct. 127, 1 936 UNITED STATES PATENT OFFICE ELECTRIC CONTACTING MEMBER Franz it. Hensel, Indianapolis, Ind., assignor, by mesne assignments, to P. It. Mallory 8: Co., Inc., Indianapolis, 11141., a corporation of Delaware No Drawing. Application September 4, 1935,

Serial No. 39,128

Claims. (Cl. 2194) This invention relates to electrical contacting members and the like, such as welding electrodes,

forth in my copending application, Serial Number 28,303, filed. June 25, 1935.

An object of the invention is to improve the strength, hardness and temperature-resistant properties of contacting elements of the type disclosed.

Another object is to improve the electrical l5 characteristics of such elements, including their arc-snuffing properties.

Further objects are to prevent oxidation of the contacting elements both during 'and after formation thereof.

A specific object is to produce contacting elements, such as welding electrodes, contacts, trolley shoes and wheels and electrical contacts generally.

The present invention comprises the combina tion of elements, methods of manufacture, and the product thereof brought out and exemplified in the disclosure hereinafter set forth, the scope of the invention being indicated in the appended claims.

While a preferred embodimentof the invention is described herein, it is contemplated that considerable variation may be made in the method of procedure and the combination of elements without departing from the spirit of the invention.

The invention contemplates the provision of a contacting element formed of an alloy of copper,

chromium, zinc and silicon. This alloy, while generally lower in electrical conductivity than the no ccpper-chromium-zinc alloy of my co-pending application, S. N. 28,303, is characterized by a very high strength and hardness as well as by its non-corroding properties.

The completed copper-chromium-zinc-silicon contacting element, to have the most desirable characteristics, should contain the component ingradients in the following ranges of proportions:

Zinc: 0.1 'to 5.0% Chr 0.1 to 2.5% Silicon 0.05 to 5.0% Copper- Balance For a number of applications it has been found a best to lteep the proportions of zinc and ofchromium below 1% for each, the following compositions being typical.

(a) Chromium 0.5%

Zinc 0.5%

' Silicon 0.18%

Copper Balance (0) Chromium 0.5%

Zinc 0.5%

Silicon 0.25% Copper Balance In other instances percentages of zinc of 1% or higher are advantageous, as in the following composition found especially suitable where high arcsnumng ability is required.

In cases where high hardness and corrosion resistances are required a higher silicon content may be used such as given below:

(d) Chromium 0.5% Zinc 1.5% Silicon 2.0% Copper Balance In the further treatment of the alloy after solidification it may be first heated to a temperature of 600 C. to 1050" C., and preferably above 700 C. for a short time, such as from 10 to 30 minutes. After the metal has reached the desired temperature it may be cooled quickly from the high temperature (quenched). The next step is preferably to heat treat the quenched alloy at a temperature of 350 C. to 600 C. for a period of from 10 minutes to 30 hours, depending on'the temperature, the percentage of hardener used, and the results desired.

The alloy may then be cold worked to obtain a cold reduction of approximately 20% and further cold reduction up to 50% or more may be applied to further increase the hardness.

For maximum hardness and conductivity, however, it is preferable to apply a series of cold reductions alternated with relatively low temperature heat treatment, preferably within the range 400 C. to 500 C. The number of cold workings with intermediate heat treatments may vary with the properties desired in the finished product.

Instead of cold working the alloys they may be hot forged according to usual methods and it will be found that the resulting hot-forged product will also have a hardness greater than the alloys of the prior art.

The present alloy is notable for its heat resistance properties after aging and cold reduction. The hardness and electrical conductivity are maintained indefinitely in temperatures in the order of 400 C. to 475 C.

The presence of the zinc likewise tends to prevent excessive surface oxidation in the finished, solidified alloy and is particularly advantageous where it is heated to high temperatures. The surface oxidation in copper-chromium-silicon alloys is quite serious since the oxygen penetrates along the grain boundaries and tends to make the alloy brittle. In the present alloy, the chromium and silicon are protected by the zinc. which will oxidize in preference to these elements.

The alloy likewise has improved arc-snumng properties due to the presence of the zinc. This is highly advantageous for the electrical applications, such as in the use of the alloy tor pressure welding electrodes and as a contact material. The low-boiling zinc (930 C.) tends to produce a gaseous phase which extinguishes the arc. These arcing characteristics are improved by increasing the proportions of zinc.

This alloy is further characterized by small grain size. Copper-chromium materials must be heated to above 900 C. before quenching in water. That elevated temperature, however, is normally very conducive to grain growth, the size of the grains usually depending on the length of time the material is held at the elevated temperature. With the present alloy containing zinc, the grain size appears to be considerably reduced from that found in other copper-chromium alloys.

In the present alloy the proportions of zinc are kept below 5% and accordingly no low-melting point phase is formed, such as that formed in alloys containing zinc in high proportions. This allows a wider range of forging or hot workingv temperatures and presents a decided improvement over such alloys as copper-chromiumcadmium in which the forging range is very small.

While the present contacting element has an electrical conductivity lower than that of the alloy covered by my copending application, Serial Number 28,303, the strength and hardness are much higher due to the silicon content.

The contacting element of the present invention can be so formed as to be adapted for use in resistance welding electrodes, contacts and the 5 like. v

While the present invention, as to its objects and advantages, has been described herein as carried out in specific embodiments thereof, it is not desired to be limited thereby but it is in- 10 tended to cover the invention broadly within the spirit and scope of the appended claims.

What is claimed is:

1. A welding electrode composed of 0.1 to 5.0%

zinc, 0.1 to 2.5% chromium, 0.05 to 5.0% silicon l6 and the remainder copper.

2. A welding electrode composed of about 0.1 to 5.0% zinc, 0.1 to 2.5% chromium, 0.05 to 5.0% silicon and the remainder substantially all copper, A characterized by high hardness, high are 20 snuiiing ability, and by the ability to maintain its hardness and electrical conductivity at temperatures in the order of 400 C.

3. An electric contacting member of the class comprising welding electrodes and electrical 25 make-and-break contacts composed of about 0.1 to 5.0% zinc, 0.1to 2.5% chromium, 0.05 to 5.0% silicon and the remainder substantially all copper, characterized by a combination of high hardness, high are snufllng ability and the ability .30

to maintain its hardness and. electrical conductivity at temperatures in the order of 400 C.

4. An electric contacting member-of the class comprising welding electrodes and electrical make-and-break contacts composed of about 0.1

ability and the ability to maintain its hardness and electrical conductivity at temperatures in the order of 400 C. v

5. An age hardened electrical contact element containing about 0.1 to 5.0% zinc, 0.1 to

2.5% chromium, 0.05 to 5.0% silicon and the remainder substantially all copper, characterized by the combination of high hardness and good electrical conductivity.

FRANZ R. HENBEL. 

